Find all School-related info fast with the new School-Specific MBA Forum

It is currently 31 Jul 2015, 01:58
GMAT Club Tests

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Machine A produces bolts at a uniform rate of 120 every 40

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 02 Dec 2012
Posts: 178
Followers: 3

Kudos [?]: 890 [0], given: 0

Machine A produces bolts at a uniform rate of 120 every 40 [#permalink] New post 07 Dec 2012, 03:03
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

90% (02:07) correct 10% (01:40) wrong based on 489 sessions
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56
[Reveal] Spoiler: OA
Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 28781
Followers: 4592

Kudos [?]: 47368 [1] , given: 7123

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink] New post 07 Dec 2012, 03:05
1
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
Walkabout wrote:
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56


Machine A produces 120/40=3 bolts per second;
Machine B produces 100/20=5 bolts per second.

Running simultaneously, they produce 3+5=8 bolts per second, thus it will take them 200/8=25 seconds to produce 200 bolts.

Answer: B.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis ; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) ; 12. Tricky questions from previous years.

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

GMAT Club Premium Membership - big benefits and savings

Manager
Manager
avatar
Joined: 30 Mar 2013
Posts: 140
Followers: 0

Kudos [?]: 23 [0], given: 196

GMAT ToolKit User
Machine A produces bolts at a uniform rate of 120 [#permalink] New post 12 Nov 2013, 07:49
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56


why cant i do it this way:
take 1/time taken for each machine to produce 20 bolts: thats (1/60) for A plus (1/100) for B. Then I add them up and take the reciprocal to get total time taken. thats 37.45. so its 37.45 bolts every 20 secs. so that 106.8 seconds for 200 bolts.

whats wrong with what I did?
Current Student
avatar
Status: busyness school student
Joined: 09 Sep 2013
Posts: 416
Location: United States
Schools: Tepper '16 (M)
GMAT 1: 730 Q52 V37
Followers: 14

Kudos [?]: 267 [0], given: 143

Premium Member
Re: Machine A produces bolts at a uniform rate of 120 [#permalink] New post 12 Nov 2013, 08:06
Machine A produces 120 bolts every 40 seconds.
How many bolts does Machine A produce every second?
Machine A produces 120/40 = 3 bolts every second.

Machine B produces 100 bolts every 20 seconds.
How many bolts does Machine B produce every second?
Machine B produces 100/20 = 5 bolts every second.

Together, Machine A and Machine B produces 3+5 = 8 bolts every second.

8 bolts / 1 sec = 200 bolts / x sec

Cross multiply, and get 200 = 8x; so, 25 = x.
So it takes 25 seconds to produce 200 bolts, when Machine A and Machine B work together.




Quote:
why cant i do it this way:
take 1/time taken for each machine to produce 20 bolts: thats (1/60) for A plus (1/100) for B. Then I add them up and take the reciprocal to get total time taken. thats 37.45. so its 37.45 bolts every 20 secs. so that 106.8 seconds for 200 bolts.


Unfortunately, I'm having trouble following your logic. It looks like you try to find how much time it takes to produce 20 bolts, but then later try to figure out how many bolts are produced every 20 seconds?
_________________

My review of some of the CAT practice exams
You can usually find me on gmatclub's chat.

Manager
Manager
avatar
Joined: 30 Mar 2013
Posts: 140
Followers: 0

Kudos [?]: 23 [0], given: 196

GMAT ToolKit User
Re: Machine A produces bolts at a uniform rate of 120 [#permalink] New post 12 Nov 2013, 08:23
I apply the simple formula: 1/(time taken by machine A) + 1/(time taken by machine B) = 1/(total time taken by both machines, together. this is now the rate (together). to get total time taken, inverse it. but i see what i did. i started adding the total bolts, thinking thats the time. i see my error, thank you. but the formula mentioned above (in my post) is correct, right?
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 28781
Followers: 4592

Kudos [?]: 47368 [0], given: 7123

Re: Machine A produces bolts at a uniform rate of 120 [#permalink] New post 12 Nov 2013, 09:12
Expert's post
usre123 wrote:
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56


why cant i do it this way:
take 1/time taken for each machine to produce 20 bolts: thats (1/60) for A plus (1/100) for B. Then I add them up and take the reciprocal to get total time taken. thats 37.45. so its 37.45 bolts every 20 secs. so that 106.8 seconds for 200 bolts.

whats wrong with what I did?


Merging similar topics. Please refer to the solution above.

Also, please search before posting.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis ; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) ; 12. Tricky questions from previous years.

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

GMAT Club Premium Membership - big benefits and savings

Manager
Manager
avatar
Joined: 07 Apr 2014
Posts: 147
Followers: 1

Kudos [?]: 11 [0], given: 81

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink] New post 11 Sep 2014, 05:35
Walkabout wrote:
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56













Machine A .. 120 in 40 seconds then 3 /sec
machine B .. 100 in 20 seconds then 5/sec

in one sec both can produce 8.

so for 200 , 200/8 = 25
2 KUDOS received
SVP
SVP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1859
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 23

Kudos [?]: 1010 [2] , given: 193

Machine A produces bolts at a uniform rate of 120 every 40 [#permalink] New post 30 Sep 2014, 22:16
2
This post received
KUDOS
Time required = \(\frac{200}{\frac{120}{40} + \frac{100}{20}} = \frac{200}{8} = 25\)

Answer = B
_________________

Kindly press "+1 Kudos" to appreciate :)

Machine A produces bolts at a uniform rate of 120 every 40   [#permalink] 30 Sep 2014, 22:16
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic Two identical machines have the ability to produce both nuts and bolts Patronus 4 15 Jun 2015, 23:18
3 Experts publish their posts in the topic Running at the same rate, 8 identical machines can produce 560 papercl Bunuel 5 27 Feb 2015, 05:01
3 Experts publish their posts in the topic Machines X and Y produce bottles at their respective constant rates. Safiya 11 29 Aug 2010, 19:43
2 Experts publish their posts in the topic Machine A produces pencils at a constant rate of 9,000 pencils per hou nitinneha 9 04 Apr 2007, 16:09
Experts publish their posts in the topic Running at the same constant rate, 6 identical machines can produce a sushom101 10 29 Oct 2005, 12:56
Display posts from previous: Sort by

Machine A produces bolts at a uniform rate of 120 every 40

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.